The present invention relates generally to inflatable structures and, more particularly to wings with inflatable aerodynamic surfaces.
Inflatable wings have been proposed for use in high altitude research vehicles as well as for use in lightweight aircraft where weight reduction is highly preferred. One such inflatable wing is disclosed in U.S. Pat. No. 3,957,232 wherein a wing structure is formed from a series of cylindrical pressure tubes which are inflatable to high pressure to deploy the structure from its stored, collapsed condition. Varying cylinder diameters yield aerodynamically curved surfaces which are covered with a thin collapsible material, such as Mylar.RTM., to define a smooth, taut wing surface.
The aforesaid and other prior art wings have numerous disadvantages, one such disadvantage being that the structural rigidity or resistance to bending during loading is dependent upon high inflation pressures. Maintenance of high pressure in such inflatable wing structures is difficult and becomes increasingly more difficult as the required pressure level increases.
Since the pressure tubes in the aforesaid prior art wing extend from the wing leading to trailing edge to define the airfoil profile, overall weight is unnecessarily increased. This weight problem is exacerbated by the fact that each individual pressure tube is of constant diameter along the spanwise axis, i.e., from the wing root to the wing tip, which I have found to be unnecessary from a structural standpoint since the wing behaves as a cantilever beam and therefore the bending moment (i.e., wing loading) progressively decreases from a maximum value at the root to zero at the tip.
It is accordingly one object of the present invention to provide an inflatable pressure aircraft wing capable of structural wing loading at relatively low inflation pressures.
Another object of the invention is to provide an inflatable wing with inflatable pressure tubes which are provided with stiff reinforcement materials for primary load bearing capability along the wing spanwise axis such that said reinforced inflatable pressure tubes behave structurally as an I-beam or a box beam.
Still a further object is to provide an inflatable tube arrangement with stiff reinforcement materials collapsible along the spanwise axis upon deflation of said tubes.
Yet another object is to provide an inflatable wing in which primary structural load bearing capability along the spanwise axis is provided by an inflatable I-beam-like construction of two attached inflatable tubes connected together by top and bottom reinforcement members collapsible in the spanwise direction.
Yet a further object is to provide an inflatable wing in which the tubes are conically tapered, having maximum diameters proximate the wing root where maximum loading occurs, and minimal diameters proximate the wing tip where wing loading is minimal, said conical tapered tubes resulting in reduced wing weight without loss of structural capability of the cantilevered wing configuration.
Yet another object is to provide an inflatable wing wherein the tubes are designed to resist torsional forces that may cause wing flutter during flight.